Chewing gums of the types typically known in the art contain many ingredients including flavor ingredients, sweetener ingredients and flavor-enhancing ingredients. It is often desirable to produce a chewing gum having a high degree of sweetness and flavor, which lasts for an extended period of time. "Fast release" chewing gums known in the art typically release their flavor and sweetness compounds rapidly, creating an initial burst of high intensity sweetness and flavor which is pleasing to the consumer but which does not last. "Slow-release" chewing gums, on the other hand, release their sweetness and flavor over a longer period of time but do not provide an initial burst of high intensity sweetness and flavor. Hence, chewing gum manufacturers are constantly trying to extend the time in which consumers can enjoy the sweetness and flavor of chewing gum without sacrificing the quality of the initial sweetness and flavor impact.
In order to control the release of the flavoring agents, and thus lengthen the duration of the flavor, various methods and systems for encapsulating flavoring agents in matrices have been developed. U.S. Pat. No. 4,978,537, issued to Song, discloses gradual release structures formed by meltspinning a mixture of an active agent and a wall material. Possible active agents include high intensity sweeteners such as aspartame, alitame, acesulfame-K and its salts. Possible active agents also include inorganic salts such as sodium chloride and potassium chloride, bases, breath fresheners, flavor modifiers, etc. The wall material is preferably a material which will stretch, deform or flatten under pressure including, for instance, polyvinyl acetate but not including high molecular weight polyvinyl acetate.
U.S. Pat. No. 2,290,120, issued to Thomas, discloses the mixing of particles of chewing gum base with the flavoring agent to provide a substantially homogeneous mixture. U.S. Pat. No. 2,596,852, issued to Heggie, discloses chemically reacting the chewing gum base with molecules of flavor ingredient, wherein the chewing gum base is a vinyl acetate polymer and the flavor molecule contains an ethylenic bond.
U.S. Pat. No. 2,886,446, issued to Kramer, discloses the coacervation of a typically volatile, water immiscible flavoring oil within a body of gelatin. U.S. Pat. No. 3,085,048, issued to Bush, discloses a process for coating dicalcium phosphate with sugar. U.S. Pat. No. 3,795,744, issued to Ogawa et al., discloses the coating, encapsulation or combination of flavoring agents with high molecular weight compounds including starches, cellulose, proteins, gums, polyvinyl alcohol and polyvinyl esters. U.S. Pat. No. 3,826,847, issued to Ogawa et al., contains a similar disclosure. U.S. Pat. No. 3,818,107, issued to Yolles, discloses flavoring agent appended to a polymer backbone, releasable upon hydrolysis.
U.S. Pat. No. 3,962,463, issued to Witzel, discloses the encapsulation of flavor ingredients in gelatin waxes, polyethylene and the like followed by the depositing of the encapsulated flavor particles on the surface of the chewing gum. U.S. Pat. No. 4,217,368, issued to Witzel et al., discloses the controlled release of a (second) sweetener which is dispersed in, enveloped by, trapped in and otherwise protected by the gum base. A first sweetener, which is relatively unprotected, provides an initial burst of flavor. U.S. Pat. No. 4,259,355, issued to Marmo et al., discloses a hydrolytically releasable flavor oil entrapped in gelatine, dextrin, gum acacia or modified food starch with the aid of a hydroxypropylcellulose solid suspending agent. A hydrophobic unconfined flavor oil provides an initial burst of flavor.
U.S. Pat. No. 4,230,687, issued to Sair et al., discloses the encapsulation of flavoring agent in a polymeric medium using rigorous and intimate conditions of mechanical shear to mix the flavoring agent with the encapsulating medium. The flavoring agent is gradually released from the encapsulating matrix at a rate dependent upon the rate of hydration of the matrix, which in turn depends upon the particular matrix used. The polymeric matrix may be derived from natural substances such as casein, a gelatin, modified starches, gums and related materials.
U.S. Pat. No. 4,590,075, issued to Wei et al., discloses a flavor and sweetener delivery system including a flavoring agent and/or sweetener encapsulated in an elastomeric matrix. The elastomeric matrix is substantially hydrophobic and includes elastomer, elastomer solvent, a wax system and an excipient. The excipient, which is present only in small amounts, can include carbohydrate materials (including partially hydrolyzed starch), polyhydric alcohols, and mixtures of carbohydrates and polyhydric alcohols.
Some encapsulation methods known in the art involve the use of polyvinyl acetate as a primary encapsulating material. U.S. Pat. Nos. 4,721,620 and 4,794,003 to Cherukuri et al., and U.S. Pat. No. 4,915,918 to Faust et al., disclose gum bases which contain mixtures of high molecular weight polyvinyl acetate and medium molecular weight polyvinyl acetate. In particular, the use of high molecular weight polyvinyl acetate offers a release profile which can delay the release of the encapsulated ingredient until later in the chew. However, problems have been encountered with the processing of polyvinyl acetate during the encapsulation process.
In particular, encapsulation of flavors and flavor enhancers into higher molecular weight polyvinyl acetate using common extrusion processes can cause it to plasticize. Build-up of the encapsulation mixture in the feed throat of the extruder occurs, resulting in lower throughput. Problems also occur during the cooling, grinding and sizing of the extrudate. The extrudate is extremely soft and pliable when cooled. This softness manifests itself as surface stickiness, which causes the extrudate to stick to itself.